Transgenic expression of a putative calcium transporter affects the time of Arabidopsis flowering
PPF1 is a gibberellin-induced, vegetative growth-specific gene, first isolated from short-day (SD)-grown G2 pea plants. In the current work, we found that transgenic Arabidopsis plants overexpressing the PPF1 gene (PPF1 (+)) flowered much later and had a significantly longer lifespan compared to control plants, whereas suppression of this gene (PPF1 (–)) resulted in a very rapid reproductive cycle. Western blotting analyses of PPF1 (+) and (–) plant lines revealed a positive correlation between the amount of antibody-reactive protein and the time of flowering. Green flourescent protein (GFP) co-expression assays showed that the PPF1 protein is likely localized in chloroplast membranes. Transgenic expression of PPF1 affected the calcium storage capacities since chloroplasts isolated from PPF1 (+) plants contained high Ca2+ levels while chloroplasts of PPF1 (–) plants contained very low amounts of calcium ion. Using Novikoff human hepatoma cells, we demonstrated that expression of PPF1 leads to a significant inward calcium ion current that was absent in untransformed cells. We conclude that, as a putative calcium ion carrier, PPF1 affects the flowering time of higher plants by modulating Ca2+ storage capacity within chloroplasts.
Document Type: Research Article
Affiliations: 1: College of Life Sciences, Peking University, Beijing 100871, China, 2: Laboratory of Molecular Developmental Biology, Institute of Developmental Biology, Chinese Academy of Sciences, Beijing 100080, China
Publication date: January 1, 2003